An understanding of the mechanisms involved in the cytoplasmic control of protein synthesis is essential for an understanding of the initiation of embryogenesis. For instance, the sea urchin egg passes from a state of low synthetic activity before fertilization to one of high synthetic activity after fertilization. The stimulation of protein synthesis occurs without synthesis of new messenger RNA and without synthesis of new ribosomes. Messenger RNA and ribosomes are made during oogenesis and stored in the egg in some unknown manner, ready for recruitment into polyribosomes within ten minutes after fertilization. The initial phase of my proposed research is to determine if protein synthesis is restricted at the level of polypeptide chain elongation and/or at the level of polypeptide chain initiation. The second phase of this study is the quantitative measurement of the amounts of active ribosomes and of active mRNA in unfertilized eggs as compared to embryos. The third phase is the investigation of the molecular basis of the control processes found in the first phases of the research. We found that efficiency of protein synthesis increased 2.5-fold immediately after fertilization of sea urchin eggs (Nature 278 469-471, 1979); that is the rate of polypeptide elongation increases.